In a madcap effort to get something made for Scoochmaroo's papercraft contest and my inability to do anything the easy way, I've gone and made a quasi-lifesize Koopa Troopa based on the Super Mario Galaxy version. Since this wasn't a painting competition, he's done in basic white, and later I will do a "Painting your quasi-lifesize Koopa Troopa Papercraft" instructable during which time you can continue being amazed at how difficult one person can make their own life. So, here goes:
So we start with the game model. This format is called an MTL, and to be honest, I have no idea how to work with this format to save my life. But a handy little program called Crafty can open them, revealing an odd wireframe reminiscent of nothing in particular. Why is this important? Well, you can use Crafty to export the file into a format we can actually use. Export it as an OBJ file, and save it where you can find it.
Now you'll need to check out your model and make sure it's feasible for a real world application. Game models tend to have overlapping sections to allow for character movement, but your papercraft isn't going anywhere unless you are REALLY talented. I use a 3D editor called "Art of Illusion" to mess with the models, and to be honest, 90% of it's guess work and overuse of the "undo changes" button. Anyway, when your done, save your work under another name so you still have access to the original file if you find out it won't work.